Adopting Power over Ethernet

Ethernet has become a comfortable technology for users around the world. It will inevitably dominate the manufacturing plant floor. However one aspect of Ethernet – Power over Ethernet (PoE) – is a less understood aspect of this popular networking technology whose role on the plant floor is still uncertain.

By Ed Nabrotzky, Molex Inc.

03/01/2009

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Ethernet has become a comfortable technology for users around the world. It will inevitably dominate the manufacturing plant floor. However one aspect of Ethernet %%MDASSML%% Power over Ethernet (PoE) %%MDASSML%% is a less understood aspect of this popular networking technology whose role on the plant floor is still uncertain.

PoE is a method of transmitting electrical power and data to remote devices over a network. Telephones, IP cameras or desktop will have only one cable to supply both data and power. The convenience and cost savings of PoE are already generating tremendous growth in consumer and office products. Many of those same advantages could be realized in factory floor installations as well. As Ethernet comes to the plant floor, will PoE come with it?

Some early adopters in manufacturing are experimenting with PoE to achieve these benefits. Since there are no industry standards or certification for powered industrial Ethernet, many companies are experimenting with competing hybrid approaches. One is often described as Ethernet over Power (EoP): a method of multiplexing data over existing power lines. Another is coined Power and Ethernet (P&E): a method using separate conductors and hybrid connectors to carry both signal and power through one wire %%MDASSML%% albeit isolated from each other on separate conductors. Each is establishing an early niche in manufacturing. Eventually one must emerge as the standard. If a company is interested in improving installation and maintenance of communications networks on the plant floor in the future, which powered Ethernet solution should they choose?

Economic impact of adoption

Economic conditions are probably impacting the adoption of Ethernet generally on the plant floor by three to five years due to reaction to this downturn. With many projects and investment in the future largely on hold, we are seeing a temporary return to legacy technology. This means that companies are reverting to an “ain’t broke, don’t fix it” mode to optimize use of scarce resources. In many cases, engineers assigned to future designs have been let go or reassigned. Out of necessity, many are sticking with what is generating revenue now and not investing in technologies that will reap benefits down the road. As a result, the commercial world will have some additional time to further innovate and for users to get more comfortable with powered networking before plant floors need to adopt this hybrid technology.

Users are already getting very comfortable plugging in power data devices because it’s simple and easy. Soon, automation engineers experiencing this convenience at home and in the office will require industrial manufacturers to create similar powered sensors, instrumentation and devices to make their factory lives easier. It makes sense that simple sensors, devices and instrumentation will be using powered networking in the future.

Cost effective

One of the main drivers in the adoption of PoE is cost savings. It’s more cost-effective to run one cable to a device. The install time is greatly reduced. Device manufacturers can save by removing a connector from their device. Replacement time is reduced by being able to unplug a device when it malfunctions and plug a new one back in.

A good example is vision systems, where virtually all cameras in the commercial and business world are PoE-enabled due to their typically simple remote installation requirements. As commercial manufacturers modify their offerings for the factory floor, they are leaving in place the PoE interface.

Process industries are also starting to adopt PoE %%MDASSML%% along with a healthy growth in wireless %%MDASSML%% because of the expense of long data and power cable runs. The technology is available for these applications; the ease of use and cost savings are clear.

But what about high-powered devices and more process-critical components such as motion systems? This set of applications is the largest part of industrial automation and makes everything move. It also typically requires greater power levels than simple instrumentation. For greater power usage devices (more than 60 W), there is no viable PoE technology available today. Other approaches such as EoP or P&E may ultimately be more suitable and are being experimented with in European automotive consortiums.

As consumers, we understand very clearly the benefits of having power and data united in one point of connection. With more people using the technology in the consumer world, adoption will be faster on the plant floor %%MDASSML%% extending the application of technology. Device manufacturers and network planners should be considering their powered architecture as they move to Ethernet for the future.

Author Information

Ed Nabrotzky is a group product manager for Industrial Communication at Molex Inc. (

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